Bottom Line:
Mineralized and non-mineralized coatings were found extensively in the porous trabecular bone of a variety of dinosaur and mammal species across time.Blood cell size iron-oxygen spheres found in the vessels were identified as an oxidized form of formerly pyritic framboids.Our observations appeal to a more conservative explanation for the structures found preserved in fossil bone.

Affiliation: Department of Paleontology, Burke Museum of Natural History, Seattle, Washington, United States of America. tomkaye@u.washington.edu

ABSTRACTA scanning electron microscope survey was initiated to determine if the previously reported findings of "dinosaurian soft tissues" could be identified in situ within the bones. The results obtained allowed a reinterpretation of the formation and preservation of several types of these "tissues" and their content. Mineralized and non-mineralized coatings were found extensively in the porous trabecular bone of a variety of dinosaur and mammal species across time. They represent bacterial biofilms common throughout nature. Biofilms form endocasts and once dissolved out of the bone, mimic real blood vessels and osteocytes. Bridged trails observed in biofilms indicate that a previously viscous film was populated with swimming bacteria. Carbon dating of the film points to its relatively modern origin. A comparison of infrared spectra of modern biofilms with modern collagen and fossil bone coatings suggests that modern biofilms share a closer molecular make-up than modern collagen to the coatings from fossil bones. Blood cell size iron-oxygen spheres found in the vessels were identified as an oxidized form of formerly pyritic framboids. Our observations appeal to a more conservative explanation for the structures found preserved in fossil bone.

pone-0002808-g006: Iron mineralization in vascular canal.SEM image of fractured bone surface across canal. Bottom half is EDS overlay with red representing a mineralized iron coating and green, calcium from the original bone. The transition from bone to coating is not immediately apparent without elemental analysis. UWBM 89326 Scale bar, 10 µm.

Mentions:
The arrows in Fig. 5 identify coatings that peeled away from the bone when fractured, revealing a layered structure. Figure 6 shows an SEM image of a typical vascular canal in the upper half of the image. The bottom is overlaid with an elemental map showing the presence of iron (shown in red) within the coating of the vascular canal, and the presence of calcium (shown in green) in the bone itself. This picture illustrates the difficulty of identifying the layering in a standard image and may have contributed to these coatings not being identified in the past. All of the Lance and Hell Creek specimens collected from both the surface and several meters deep in quarries, showed some evidence of this coating. Most were iron-infiltrated but some contained only carbon and were not mineralized.

pone-0002808-g006: Iron mineralization in vascular canal.SEM image of fractured bone surface across canal. Bottom half is EDS overlay with red representing a mineralized iron coating and green, calcium from the original bone. The transition from bone to coating is not immediately apparent without elemental analysis. UWBM 89326 Scale bar, 10 µm.

Mentions:
The arrows in Fig. 5 identify coatings that peeled away from the bone when fractured, revealing a layered structure. Figure 6 shows an SEM image of a typical vascular canal in the upper half of the image. The bottom is overlaid with an elemental map showing the presence of iron (shown in red) within the coating of the vascular canal, and the presence of calcium (shown in green) in the bone itself. This picture illustrates the difficulty of identifying the layering in a standard image and may have contributed to these coatings not being identified in the past. All of the Lance and Hell Creek specimens collected from both the surface and several meters deep in quarries, showed some evidence of this coating. Most were iron-infiltrated but some contained only carbon and were not mineralized.

Bottom Line:
Mineralized and non-mineralized coatings were found extensively in the porous trabecular bone of a variety of dinosaur and mammal species across time.Blood cell size iron-oxygen spheres found in the vessels were identified as an oxidized form of formerly pyritic framboids.Our observations appeal to a more conservative explanation for the structures found preserved in fossil bone.

Affiliation:
Department of Paleontology, Burke Museum of Natural History, Seattle, Washington, United States of America. tomkaye@u.washington.edu

ABSTRACTA scanning electron microscope survey was initiated to determine if the previously reported findings of "dinosaurian soft tissues" could be identified in situ within the bones. The results obtained allowed a reinterpretation of the formation and preservation of several types of these "tissues" and their content. Mineralized and non-mineralized coatings were found extensively in the porous trabecular bone of a variety of dinosaur and mammal species across time. They represent bacterial biofilms common throughout nature. Biofilms form endocasts and once dissolved out of the bone, mimic real blood vessels and osteocytes. Bridged trails observed in biofilms indicate that a previously viscous film was populated with swimming bacteria. Carbon dating of the film points to its relatively modern origin. A comparison of infrared spectra of modern biofilms with modern collagen and fossil bone coatings suggests that modern biofilms share a closer molecular make-up than modern collagen to the coatings from fossil bones. Blood cell size iron-oxygen spheres found in the vessels were identified as an oxidized form of formerly pyritic framboids. Our observations appeal to a more conservative explanation for the structures found preserved in fossil bone.